This invention relates to the repair of turbine engine components, and, more particularly to the repair of a damaged gas turbine engine stationary vane assembly.
Stationary vane assemblies for use in the hot operating turbine section of a gas turbine engine typically are subjected to excessive wear or damage during engine operation or damaged during manufacture. Such an article, sometimes referred to as a turbine nozzle or turbine nozzle assembly, typically includes at least one airfoil as well as passages and openings for air-cooling. During engine service operation in such engine location, the stationary vane assembly experiences high temperature, strenuous environmental conditions. As a result, damage can occur to the extent that repair or replacement of the assembly is required for safe, efficient operation. As is well known in the art, such air-cooled turbine components are relatively expensive to manufacture because they are complex in design and made of relatively expensive materials, for example high temperature superalloys. Therefore, it has been a practice to repair rather than to replace such a component.
Reports of methods and apparatus for repair of turbine engine stationary vane assemblies include U.S. Pat. No. 4,305,697—Cohen et al. (patented Dec. 15, 1981) and U.S. Pat. No. 5,758,416—Reverman et al. (patented Jun. 2, 1998). During the repair of such a turbine vane assembly, it is important to maintain the relative positions of assembly members such as the airfoils and the spaced-apart inner and outer bands between which the airfoils are secured. In one type of such repair, the inner and outer bands and the airfoils first are disassembled for the repair and/or replacement of such individual members. In that repair, re-assembly of new or repaired members to provide a repaired assembly is similar to original manufacture of the vane assembly. It includes joining of the ends of individual airfoils to the spaced-apart bands, for example by brazing or welding about airfoil end stubs, while all of such members are maintained in accurate relative positions. Such a repair can provide a number of joints with joint construction not originally designed into the article. In another type of repair, joints are at or in the vicinity of a structural support such as a flange.
It is desirable to provide a method for repairing a turbine engine stationary vane assembly that requires, in combination, a reduced number of members, joints particularly away from structural supports, and repair steps to result in a repaired assembly with enhanced structural integrity in that portion of a band adjacent the airfoil.